You are right. Perhaps we should reserve the right to charge a small fee say a few dollars where the upgrade involves substantial work. A lot of the upgrades won't because we have spent a lot of time over the last six months overhauling our conversion routines. But now that I reflect on it changes like mounted ops will involve the creation of new units - ie the leg and transport component of mech inf units. We will have to write special code to handle that. I'll ponder this some more.
For what it's worth, mounted ops can serve as a basis for a number of transport operations.
There's a component about a unit being carried that is universal, and a component about the type of carrier that is unique to equipment doing the job.
If done effectively, designing some of the mounted operations software components for the Eastern Front would serve as a foundation for future changes enabling helicopter transport, or water transport when those types of equipment and attributes are added to Estabs.
In a similar manner, river crossing has components which would also be applicable to seaborne assault operations.
And, if off-map artillery is done, it has components which support seaborne assaults, and carpet bombing.